Tuesday, May 31, 2011

I realize this is the South, and we're one day from the start of meteorological summer (June 1-Aug. 31), but don't fool yourself into thinking this week's heat wave is nothing out of the ordinary.

It is out of the ordinary.

And in a strange way, it's almost a mirror opposite of what happened exactly six months ago.

High pressure is building almost directly over the Carolinas, and it will bring near-record-breaking heat to the Charlotte region for the next few days. Today's forecast high of around 95 degrees isn't far from the day's record of 97, set in 1953.

And highs Wednesday and Thursday are expected to be in the ballpark of those day's records -- 98 for Wednesday (in 1918) and 99 for Thursday (in 1951). The heat likely will continue through the weekend and into next week, although there will be a slight change in the pattern.

Forecasters expect the center of high pressure to move backwards -- to the west -- a bit. That will bring more of an Atlantic Ocean flow into the Carolinas, which often tends to create some cloudiness and lower temperatures a few degrees. But highs are still predicted to reach 90 into next Tuesday.

So we've established that it will be hot. And, by the way, the air quality will be bad, too, because with high pressure centered over us, there will be very little air movement. That means a build-up in ozone levels, and it's the reason for our Code-Orange alert today.

A quick look at temperatures in late May and early June for the last 10 years shows nothing like this. There were a few years when Charlotte had three or four consecutive days in the 90s in early June, but nothing approached the string of seven or eight straight 90-degree days that are expected this time.

Many of those years, we had highs in the 70s in the first week of June. The average high for this time of year, by the way, is around 84.

So this is not normal.

I found it interesting how the beginning of meteorological summer was similar to the start of meteorological winter last Dec. 1.

We had warm weather through Thanksgiving, and the high temperature on Dec. 1 -- the first day of meteorological winter -- was 67 in Charlotte. Three days later, the high only reached 41, and it went downhill from there. From Dec. 4 until Valentine's Day, the Charlotte region (and nearly all of the eastern United States) had unrelenting cold and frozen precipitation.

It was as if a switch was flicked early last December, "turning on" winter.

Now it's happening with summer.

There's one other thing to watch here. Keep an eye on the location of high pressure systems over the next few weeks. That could give us an idea of where those highs will be in August and September, when tropical storms and hurricanes begin developing. The location of Atlantic high pressure plays a big role in determining if hurricanes are steered into Mexico (as was the case last year), the Gulf of Mexico (remember 2005?), or the East Coast and Florida panhandle (2004).

Friday, May 27, 2011

The Memorial Day weekend is playing out pretty much the way forecasters expected, with widespread showers and thunderstorms likely today, and then fast-improving conditions Saturday, Sunday and Monday.

Today won't be a total washout, but it won't be pretty, either.

A weak cold front has stalled over the western Carolinas, and several weak areas of low pressure will ride along the front today. The first of those crossed the Charlotte area Friday morning with heavy showers. A few more of those systems are expected to follow today.

By this afternoon, there will be enough instability in the atmosphere for those weak low pressure areas to trigger a few thunderstorms, but the storms aren't expected to be severe.

Bottom line ... today will be wet at times, with periods of dry weather mixed in. Temperatures will be cooler than in recent days, with highs only near 80. Humidity levels will be very high, however.

If you're going to Speed Street today, or to the race track walk and cookout at Charlotte Motor Speedway, be ready for occasional rainy periods.

The weak front will dissipate late tonight. On Saturday, there will be a bit of moisture and instability left behind, and it could be enough to create a few showers and thunderstorms in the afternoon. But don't fret ... most of the day will be partly sunny, and the precipitation will be widely scattered.

Temperatures will make a comeback Saturday, with highs in the middle 80s.

And by Sunday, it'll be back to the kind of weather we had earlier this week. Expect sunshine and hot temperatures, with highs near 90.

Beach weather will be outstanding, with no rain Saturday, Sunday or Monday -- and probably no rain today, either. The mountains will be rainy today, with scattered showers again Saturday. Conditions will be dry and very nice Sunday and Monday.

Thursday, May 26, 2011

We've been promising you a nice Memorial Day weekend, and it's coming ... but we'll have a bit of a rough ride over the next 24 hours.

A frontal system is moving eastward toward the Carolinas on Thursday, and it will be close enough by tonight to bring showers and thunderstorms into the area. It looks now as if the front will remain close enough to the Charlotte region to keep the stormy weather going for much of Friday.

But clearing is still expected Saturday morning, and the rest of the weekend looks good.

There might be a few isolated thunderstorms Saturday afternoon in the Piedmont and foothills, but otherwise, there'll be dry weather through Monday -- after we get through tonight and Friday. Temperatures will fall a bit Friday, amid the clouds and precipitation, but there'll be a quick recovery afterwards.

By Memorial Day, we'll be back to 90 degrees again. And mid 90s loom for next week.

A severe thunderstorm watch is in effect Thursday afternoon and evening over parts of Kentucky, Tennessee and Georgia, and the severe weather could move into the extreme western Carolinas today.

But forecasters say it'll be overnight before precipitation gets to Charlotte. The thunderstorm activity likely will diminish overnight but re-fire Friday.

We'll stay on top of this with updates as needed.

Right now, it appears as if it'll be dry and warm tonight for the Pole Night festivities at Charlotte Motor Speedway.

Wednesday, May 25, 2011

Every weekend forecast is important, but this weekend's is a lot bigger than normal for people in the Charlotte region.

And the forecast has become drier and warmer in the last 24 hours or so.

The computer models were having a tough time earlier this week trying to make heads or tails of weekend conditions, especially with a frontal system in the region and the chance of low pressure developing somewhere near the Carolinas.

Now things are coming into better focus. It looks as if the weak cold front will approach the Charlotte region Friday, then dissipate Saturday. That means Friday could be a wet day, with temperatures about 10 degrees cooler than the past few days.

Then with the front disappearing Saturday, sunshine will return. High temperatures will be in the upper 80s Saturday and Sunday, climbing into the lower 90s again Monday.

If that forecast holds, it's basically good news for the NASCAR events at Charlotte Motor Speedway. Showers and storms would arrive after Thursday night's pole qualifying and would end before the Saturday afternoon Nationwide Series race. Weather would be great for Sunday night's Sprint Series Coca-Cola 600.

And it's good news for anyone planning Memorial Day cookouts or trips to the mountains or beaches.

Monday, May 23, 2011

Technically, a heat wave for our part of the country is three or more consecutive days of 90-degree weather, and we're likely to have four straight -- starting with Sunday's reading of 91 degrees in Charlotte. That was our first 90-degree day of the year.

But most people really are curious about the upcoming Memorial Day weekend, and the outlook is ... well, cloudy.

Pat Moore, a meteorologist at the National Weather Service office in Greer, S.C., looked at the various computer models' forecasts for the weekend and said, "Confidence in the forecast falls off the cliff." In short, the computers don't agree.

The forecast for the next few days is quite confident.

High pressure is predicted to produce mostly sunny skies and daytime highs in the range of 92 or 93 degrees in the Charlotte area. Severe thunderstorms developed Sunday afternoon in the N.C. mountains and ripped across an area along and north of Interstate-40, and forecasters said they expect a few more storms today. But, they say, the storms are not expected to be as severe as those Sunday.

Any thunderstorms today are likely to remain well north of the immediate Charlotte area.

The hot and precipitation-free weather seems likely to end Thursday, when high pressure weakens over the region, allowing a frontal system to approach. And that's when the forecast gets murky.

Some of the computers predict fairly unsettled weather over the weekend. That could be bad news for fans planning to attend NASCAR races Thursday, Saturday and Sunday, and it wouldn't be good for the Food Lion Speed Streets events in Charlotte's uptown. For that matter, storms would make a mess of many people's plans to spend the Memorial Day weekend in the mountains or at the beaches.

But other computer models have a less-pessimistic forecast.

Regardless, it seems safe to expect temperatures to be a bit cooler by later in the week, and thunderstorm chances figure to climb in the area.

Tuesday, May 17, 2011

The upper-level low pressure system centered near the Grand Strand this morning is a good opportunity to look at a pair of weather phenomena affecting the Charlotte area today.

And they are conditions we see at other times in the year.

The rain showers moving slowly across the region today are mostly drifting from east to west. As most of you know, that's backwards.

Normally, precipitation in our region comes from west to east -- or southwest to northeast. Occasionally, when a "back door" cold front is dropping from the north, we'll see precipitation move from north to south. But largely, it's more of a west-to-east movement.

The counter-clockwise flow around the upper-level low today is responsible for the "backward" rain. With Charlotte to the west of the low's center, the flow around the system is bringing precipitation inland from the coast. That's something we also see later in the summer, during hurricane season.

When a tropical system is making landfall on the South Carolina coast, or even moving northward along the coastal plain, the counter-clockwise flow brings precipitation toward us from the coast.

In 2004, when the remnants of Hurricane Frances moved northward from Georgia into the western Carolinas, the Charlotte area was on the northeast side of the low. That day, showers and thunderstorms moved south to north into our region.

Some people who plan outdoors activities (attention, joggers) have learned to check the radar before starting. Today, watch to the east of Charlotte. That's where our precipitation is coming from.

Today also is a good time to talk about trends. Meteorologists have a saying, "The trend is your friend." That means when computer models or changing forecasts are following a trend, it often provides a strong hint about what is to come.

The trend in recent days has been to lower the anticipated daytime temperatures today. On Sunday, forecasts called for highs in the upper 60s today. On Monday, those forecast highs for today were dropped to the lower and mid 60s. This morning, I've seen some forecasts of a 60-degree high. This seems to happen frequently in cold-air damming events, when computer models initially underestimate how chilly it actually will be.

That said, don't be surprised if temperatures today -- which fell into the lower and mid 50s before daybreak -- don't reach 60 degrees this afternoon.

Monday, May 16, 2011

Sometimes, a system is cut off and, basically, gets stuck in a geographic area. This happens on occasion with upper-level low pressure systems, and they're commonly known as "cut-off lows."

Such a system will hover over parts of the eastern United States over the next few days, and it will bring rainy, chilly weather to the Charlotte region.

The low pressure system is crossing the Carolinas today, and it contains some cold air in the higher levels of the atmosphere. That is helping create instability, and the result will be showers and probably a few thunderstorms this afternoon.

With cold air aloft, any thunderstorm that develops could produce hail.

These cut-off lows tend to meander, since there's no jet stream to guide them along. On Tuesday, the low is expected to be somewhere over northeast North Carolina or southern Virginia. It'll still be close enough to bring us showers, and with clouds and chilly air, we'll be lucky to climb above the mid 60s in Charlotte.

That's about 15 degrees below average for this time of year.

By Wednesday, the cut-off low will drift a bit farther north, which means showers chances will diminish (but not disappear ... many areas will get another shower or two) and temperatures will reach the low 70s.

And by Thursday, the low pressure system is forecast to be far enough north and east that the Charlotte region will return to more seasonal conditions.

If you're looking ahead to Friday's and Saturday's events at Charlotte Motor Speedway, the forecast looks good. High temperatures Saturday are expected to reach the middle 80s.

Tuesday, May 10, 2011

While it won't be as stormy as today, the rest of this week and the beginning of the next could be rather wet across the Carolinas.

It appears as if stalled frontal boundaries and a series of weak low pressure systems will conspire to bring periods of showers and thunderstorms to the region. There will be some dry spells, however, and temperatures will remain on the mild side.

Today's severe weather threat is covered in another story on The Observer's website today, but once the storms move southeast of the region early Wednesday, we should enjoy rather dry conditions on Wednesday and Thursday.

A stalled frontal system will be south and west of Charlotte, so we'll see only a few scattered afternoon and evening storms both days.

By Friday, however, the computer models are hinting at an upper-level low pressure system moving slowly into the Carolinas. That could bring several days of unsettled weather ... marked by mostly cloudy skies and periods of showers and storms. It could last through the weekend and into next Monday or Tuesday.

The scenario we talked about in late March seems to be playing out ... chilly air has been parked over the North for much of the spring, and the dividing line between colder conditions and the warmth of the South has served as a focus for stormy weather. It could be a couple more weeks before the chilly air is pushed farther north for the summer.

Wednesday, May 4, 2011

Our lawns were watered overnight, and now the rain has moved out, clearing the way for five days of glorious weather while Charlotte serves as host of the PGA's Wells Fargo Championship at the Quail Hollow Club.

Well, probably five days of glorious weather.

Today should be fine, although the golfers who tee off early in the pro-am event will do so under cloudy skies and with wet grounds to contend with.

Nearly an inch of rain fell overnight, in two rounds -- the first, with a cluster of thunderstorms that moved through the area before midnight; then, more rain from a line of heavy showers that crossed the region between 3 and 6 a.m.

The rain moved east of Charlotte around daybreak, and clearing skies began moving toward the region from the west.

By mid-morning, skies will be at least partly sunny. Temperatures, however, will be nowhere near Tuesday's 80-degree-plus readings. When the cold front passed through Charlotte early Wednesday morning, temperatures fell from near 60 to around 50 degrees. Highs this afternoon will only reach the upper 60s. That is a sign of the chilly air moving into the region for the next 48 hours.

Frost and freeze advisories have been posted tonight for the mountains, and the predicted low temperature in Charlotte is 41 degrees Thursday morning. That is close to the record for the date -- 39 degrees, set in 1973.

So if you're planning to attend the first round of the golf tournament Thursday, take a jacket along.

The rest of the week should feature partly sunny to sunny skies, with a gradual warm up. Highs will be near 70 degrees Thursday, 72 on Friday, 78 on Saturday, and then 81 on Sunday.

Two things to remember ... there will be a small chance of a shower Friday and a thunderstorm Sunday. A weak low pressure system is expected to pass to the north Friday, but it could be close enough for a shower to sneak into the Charlotte area.

And by Sunday afternoon, forecasters think there might be enough moisture and instability in the atmosphere for a few thunderstorms to develop. As of now, however, those storms appear to be widely scattered. Most areas should remain dry.

About this blog

Steve Lyttle says growing up in northeastern Ohio, with its foot-deep snows and summertime severe thunderstorms, fueled his interest in meteorology. He has written about weather for 10 years at The Observer. Join the discussion about weather trends and weird weather events -- whether local or around the world.